1. Field of the Invention
The present invention relates to a solid immersion lens and a microscope to be used for a method for inspecting electronic devices, for example, which is employed for failure analysis of electronic devices and for reliability evaluation thereof.
2. Related Background of the Invention
In an inspection of electronic devices, a method for observing an electronic device as a sample by a microscope has been employed. Conventionally, an emission microscope and an IR-OBIRCH apparatus, etc., have been known as electronic device inspection apparatuses (cf. Japanese Patent Application Laid-Open No. H7-190946 and Japanese Patent Application Laid-Open No. H6-300824). However, in recent years, miniaturization of electronic devices, which are inspected objects, has been advanced, and in prior-art inspection apparatuses employing visible light, infrared light, or heat rays, it has become difficult to analyze the microstructure due to restrictions resulting from a diffraction limit in an optical system.
Therefore, in a case where an abnormal point generated in circuit patterns such as transistors and wiring, which are formed in an electronic device, is detected by analyzing such a microstructure of an electronic device, such a method has been used, in which the range where the abnormal point exists is first narrowed to some extent by an inspection apparatus employing visible light, infrared light, or heat rays, then the narrowed range is observed by use of an observation apparatus such as an electron microscope having a higher resolution, and thereby the abnormal point in the electronic device is inspected.
As described above, in the method where a high-resolution observation is carried out by an electron microscope after an inspection using light is carried out, there is a problem in that the inspection of electronic devices requires a great deal of work and time due to such a reason, that is, preparation and installation of electronic devices of the targets of the inspection being complicated and cumbersome.
On the other hand, a solid immersion lens (SIL) has been known as a lens for enlarging an image of an observed object. The solid immersion lens is generally known as a hemispherical lens or a lens with a hyperhemispherical form called a Weierstrass sphere. By installing this solid immersion lens on the surface of an observed object, both the numerical aperture NA and magnification can be enlarged, thus an observation with a high resolution becomes possible. As semiconductor inspection apparatuses using such solid immersion lenses, for example, those described in Japanese Patent Publication No. H7-18806 and the specification of U.S. Pat. No. 6,594,086 exist. In addition, description of a solid immersion lens also exists in Japanese Patent Application Laid-Open No. 2002-189000.